表面蒸气溶胶-凝胶Al2O3薄膜电极上肌红蛋白的直接电化学研究

本文利用表面蒸气溶胶-凝胶沉积与层层组装技术相结合,成功制备了溶胶-凝胶三氧化二铝(SG-Al2O3)/肌红蛋白(Mb)层层组装薄膜修饰电极({SG-Al2O3/Mb}n)。通过实验确定了最优组装方式PG/PD-DA/{SG-Al2O3/Mb(pH 5.0)}n以及在表面蒸气溶胶-凝胶沉积过程中的最佳涂布水量2μL。考察了该薄膜修饰电极的循环伏安性质。实验表明:在pH 7.0缓冲溶液中,薄膜中的Mb在-0.34 V出现了一对可逆性良好的还原氧化峰,这是血红素辅基的电活性中心Fe(III)/Fe(II)氧化还原电对的特征峰,随着缓冲溶液pH值的增长,峰电位发生负移,式量电位E°’与pH值呈直线关系,其斜率为–42.4 mV/pH,随着扫描速度的增大,峰电流增大,且电流与扫描速度的平方根成正比。     

Direct electrochemistry and electrocatalysis of myoglobin immobilized on L-cysteine self-assembled gold electrode

Myoglobin (Mb) has been successfully immobilized on a self-assembled monolayer (SAM) of L-cysteine (Cys) on a gold electrode, Au/Cys. The presence of a pair of well-defined and nearly reversible waves centered at ca. 0.086 V vs Ag/AgCl (pH 6.5) suggests that the native character of Mb heme Fe(III/II) redox couple has been obtained. The formal potential of Mb on Cys SAM exhibited pH-dependent variation in the pH range of 5-9 with a slope of 55 mV/pH, indicating that the electron transfer is accompanied by a single proton exchange. Thermodynamic and kinetic aspects of Mb adsorption processes on Au/Cys were studied by using voltammetric and quartz-crystal microbalance methods. The Au/Cys electrode with immobilized Mb exhibited electrocatalytic activity toward ascorbic acid (AA) oxidation with an overpotential decrease of over 400 mV and a linear dependence of current on the AA concentration from 0.5 to 5.0 mmol L(-1).     

肌红蛋白在海藻酸钠水凝胶中的电化学和电催化特性

海藻酸钠(Sodium Alginate,SA)是由L-葡萄糖醛酸与D-甘露糖醛酸组成的高分子线性糖醛酸,常作为固定化酶包埋材料。本文研究了海藻酸钠水凝胶膜中的肌红蛋白在磷酸盐缓冲溶液中的直接电化学和酶催化性质,探讨了测定H2O2和NO2^-的可能性。     

Direct electrochemistry of myoglobin based on bicontinuous gyroidal mesoporous carbon matrix

A strategy of protein entrapment within the bicontinuous gyroidal mesoporous carbon (BGMC) matrix is demonstrated to probe the direct electrochemistry of myoglobin. Large surface area and remarkable electro-catalytic properties of BGMC make it a suitable candidate for high loading of protein molecules and the promotion of heterogeneous electron transfer (ET). In contrast with carbon nanotubes and general carbon mesoporous materials, BGMC is of a relatively isotropic graphited structure and thus can more effectively enhance the heterogeneous ET. Furthermore, a series of BGMCs with different pore sizes (2–7 nm) is designed and synthesized to study the influence of pore size on the immobilization of redox proteins and on the electron transfer.     

Monitoring the electrochemistry of single molecules by surface-enhanced Raman spectroscopy

Coherent control of chemical species in complex systems is always subject to intrinsic inhomogeneities from the environment. For example, slight chemical modifications can decisively affect transport properties of molecules on surfaces. Hence, single-molecule (SM) studies are the best solution to avoid these problems and to study diverse phenomena in biology, physics, and chemistry. Along these lines, monitoring SM redox processes has always been a "holy grail" in electrochemistry. To date, claims of SM electrochemistry by spectroscopy have come only from fluorescence quenching of polymers and redox-fluorescent molecules. In unconnected developments, the potential of the bianalyte surface-enhanced Raman scattering (SERS) method as a technique with SM sensitivity has been demonstrated. Raman spectroscopy has the potential to explore SM detection of any molecule, independent of its chemical nature. We provide definitive proof of SM events following redox cycles using SERS. The superior sensitivity and spectral richness of SERS makes it general enough to study, in principle, SM electron transfer of any (label-free) molecule.     

Direct electrochemistry and electrocatalysis of myoglobin in dodecyltrimethylammonium bromide film modified carbon ceramic electrode

Direct electrochemistry and electrocatalysis of myoglobin（Mb） were studied with Mb immobilized on dodecyltrimethylammonium bromide（DTAB） film modified carbon ceramic（CC） electrode.Cyclic voltammetry showed a pair of well-defined and nearly reversible redox peaks of Mb（Fe^Ⅱ/Fe^Ⅲ） at about—0.3 V vs.SCE（pH = 6.98）.The currents of the redox peak were linear to scan rate,and rate constant（Ks） was estimated to be 3.03 s^-1.The formal potential（E°’） of Mb in the DTAB/CC electrodes shifted linearly with pH with a slope of -36.44 mV/pH,implying that the electron transfer between DTAB and CC electrodes is accompanied by proton transportation.The immobilized Mb exhibited excellent electrocatalytic response to the reduction of hydrogen peroxide（H₂O₂）.     

Ultrafast dynamics of myoglobin probed by time-resolved resonance Raman spectroscopy

Recent experimental work carried out in this laboratory on the ultrafast dynamics of myoglobin (Mb) is summarized with a stress on structural and vibrational energy relaxation. Studies on the structural relaxation of Mb following CO photolysis revealed that the structural change of heme itself, caused by CO photodissociation, is completed within the instrumental response time of the time-resolved resonance Raman apparatus used (approximately 2 ps). In contrast, changes in the intensity and frequency of the iron-histidine (Fe-His) stretching mode upon dissociation of the trans ligand were found to occur in the picosecond regime. The Fe-His band is absent for the CO-bound form, and its appearance upon photodissociation was not instantaneous, in contrast with that observed in the vibrational modes of heme, suggesting appreciable time evolution of the Fe displacement from the heme plane. The band position of the Fe-His stretching mode changed with a time constant of about 100 ps, indicating that tertiary structural changes of the protein occurred in a 100-ps range. Temporal changes of the anti-Stokes Raman intensity of the v4 and v7 bands demonstrated immediate generation of vibrationally excited heme upon the photodissociation and decay of the excited populations, whose time constants were 1.1 +/- 0.6 and 1.9 +/- 0.6 ps, respectively. In addition, the development of the time-resolved resonance Raman apparatus and prospects in this research field are described.     

Direct electrochemistry of myoglobin based on DNA accumulation on carbon ionic liquid electrode

Poly-anionic deoxyribonucleic acid (DNA) was accumulated on the positively charged surface of carbon ionic liquid electrode (CILE) with N-butylpyridinium hexafluorophosphate (BPPF₆) as binder, and then myoglobin (Mb) was immobilized onto the DNA film by electrostatic interaction to form Mb/DNA/CILE electrode. The direct electrochemistry of Mb was then investigated in detail. A pair of well-defined, quasi-reversible cyclic voltammetric peaks of Mb was obtained with the formal potentials (E⁰′) at ?0.304 V (vs. SCE) in phosphate buffer solution (PBS, pH 7.0). The Mb/DNA/CILE electrode showed excellent electrocatalytic activity to H₂O₂ and trichloroacetic acid (TCA) in the range of 1.0–160 μmol/L and 0.5–40.0 mmol/L, respectively. The apparent Michaelis–Menten constants (K_M) toward H₂O₂ and TCA were calculated as 0.42 and 0.82 mmol/L. So, the DNA/CILE had potential to study other proteins.     

Direct electrochemistry and electrocatalysis of myoglobin immobilized in hyaluronic acid and room temperature ionic liquids composite film

A novel biocomposite film based on hyaluronic acid (HA) and hydrophilic room temperature ionic liquid 1-ethyl-3-methyl-imidazolium tetrafluoroborate ([EMIM][BF₄]) was explored. Here, HA was used as a binder to form [EMIM][BF₄]-HA composite film and help [EMIM][BF₄] to attaching on glass carbon electrode (GCE) surface, while doping [EMIM][BF₄] in HA can effectively reduce the electron transfer resistance of HA. The composite film can be readily used as an immobilization matrix to entrap myoglobin (Mb). A pair of well-defined and quasi-reversible redox peaks of Mb was obtained at the Mb-[EMIM][BF₄]-HA composite film modified GCE (Mb-[EMIM][BF₄]-HA/GCE) through direct electron transfer between Mb and the underlying electrode. The Mb-[EMIM][BF₄]-HA/GCE showed an excellent electrocatalytic activity toward the reduction of H₂O₂. Based on the [EMIM][BF₄]-HA biocomposite film, a third-generation reagentless biosensor could be constructed for the determination of H₂O₂.     

Direct electrochemistry of myoglobin immobilized on chitosan-wrapped rod-constructed ZnO microspheres and its application to hydrogen peroxide biosensing

Rod-constructed zinc oxide (ZnO) microspheres (RZnOMs), consisting of hundreds of needle-like ZnO nanorods, were utilized to explore a novel biosensor through coupling with myoglobin (Mb) in the presence of chitosan (Chi). Biocompatibility and electrochemical properties of the resulting ZnO-Chi-Mb composite film were studied by Fourier-transform infrared spectroscopy and cyclic voltammetry. The results revealed that the RZnOMs-based composite was a satisfying matrix for proteins to effectively retain their native structure and bioactivity. With advantages of the unique inorganic material, facilitated direct electron transfer of the metalloenzymes was acquired on the RZnOMs-based enzyme electrode. Moreover, the RZnOMs-based biosensor also displayed significant electrocatalytic activity for the reduction of hydrogen peroxide with an apparent Michaelis–Menten constant (32 μM), wide linear range (2–490 μM), and low detection limit (0.21 μM, S/N = 3). These indicated that the RZnOMs were one of the ideal candidate materials for direct electrochemistry of redox proteins and related biosensor construction.     

Direct electrochemistry of hemoglobin and myoglobin at didodecyldimethylammonium bromide-modified powder microelectrode and application for electrochemical detection of nitric oxide

Hemoglobin (Hb) and myoglobin (Mb) were immobilized at the didodecyldimethylammonium bromide (DDAB)-modified powder microelectrode (PME) to fabricate Hb-DDAB-PME and Mb-DDAB-PME. Direct electrochemistry of Hb and Mb were achieved on the DDAB-modified PME. The formal potential was −0.224 V for Hb and −0.212 V for Mb (vs. SCE). The apparent surface concentration of Hb and Mb at the electrode surface was 2.83 × 10⁻⁸ and 9.94 × 10⁻⁸ mol cm⁻². The Hb-DDAB-PME and Mb-DDAB-PME were successfully applied for measurement of NO in vitro. The anodic current peaks for NO oxidation at +0.7 V and the cathodic current peaks for NO reduction at −0.85 V on the CV curves were obtained on the modified electrodes. For detection of NO at +0.7 V, the sensitivity is 3.31 mA μM⁻¹ cm⁻² for Hb-DDAB-PME and 0.6 mA μM⁻¹ cm⁻² for Mb-DDAB-PME. The detection limit is 5 nM for Hb-DDAB-PME and 9 nM for Mb-DDAB-PME. The linear response range is 9-100 and 28-330 nM for Hb- and Mb-modified PME, respectively. For the electrochemical detection of NO at −0.85 V by using Hb-DDAB-PME, the detection sensitivity is 39.56 μA μM⁻¹ cm⁻²; the detection limit is as low as 0.2 μM; and the linear response range is 1.90-28.08 μM.     

Direct electrochemistry of myoglobin on TiO2 and alginate composite modified carbon ionic liquid electrode via the electrodeposition method

Journal of Solid State Electrochemistry - In this work, electrodeposition of the mixture of myoglobin (Mb), sodium alginate (SA), and TiO2 nanoparticles on the carbon ionic liquid electrode (CILE)...     

Direct detection of 8-oxo-deoxyguanosine using UV resonance Raman spectroscopy

8-oxo-deoxyguanosine (8-oxo-dG) is a major oxidative lesion in DNA and is responsible for mutation and cancer. Current techniques for detecting 8-oxo-dG are indirect methods. Thus, development of new methodologies is needed to directly detect such oxidative lesions. In this article, we have used ultraviolet resonance Raman (UVRR) spectroscopy as a novel analytical technique for the detection of 8-oxo-dG. Here, the UVRR spectrum of 8-oxo-dG was acquired and compared to that of deoxyguanosine (dG) and deoxyadenosine (dA). Data analysis shows a distinct UVRR spectrum of 8-oxo-dG with characteristic peaks. Detection of 8-oxo-dG was easily achieved from a mixture with dG. These results reveal that UVRR spectroscopy shows promise as a direct method for detecting 8-oxo-dG.     

Direct electrochemistry of myoglobin based on electrodeposition of Pd nanoparticles with carbon ionic liquid electrode as basic electrode

We report on the direct electrochemistry and electrocatalytic properties of myoglobin (Mb) immobilized on a carbon ionic liquid electrode covered with a matrix composed of an ionic liquid, gellan gum, and Pd nanoparticles. UV-vis and FT-IR spectroscopy confirm that Mb retains its native structure in the composite film on the electrode. Scanning electron microscopy reveals that the nanoparticles are deposited on the surface of the Pd electrode. Cyclic voltametry gives a pair of well-defined and quasireversible redox peaks with a formal potential (E ^0′) of ?332 mV and a peak-to-peak separation of 64 mV at near-neutral pH value. The modified electrode shows good electrocatalytic activity towards the reduction of hydrogen peroxide, with a linear range between 5.0 μM and 0.27 mM and a detection limit of 1.7 μM (S/N = 3). The apparent Michaelis-Menten constant is 88 μM.

Application of surface-enhanced Raman spectroscopy to mechanistic electrochemistry: Oxidation of iodide at gold electrodes

The electrooxidation of dilute (1 mM) iodide at the gold-aqueous interface has been examined by rotating disk voltammetry combined with surface-enhanced Raman spectroscopy (SERS) in order to identify the surface species formed and hence to shed light on the electrooxidation mechanism. Marked changes in the SER spectra occur upon shifting the electrode potential through the region where faradaic current flows, the characteristic 123 and 158 cm⁻¹ bands associated with adsorbed iodide being supplemented and eventually supplanted by bands at 110, 145 and 160–175 cm⁻¹, the latter two being especially intense. The new bands are assigned to higher polyiodides and molecular iodine. The latter species appears to be the major interfacial product associated with faradaic current flow. Iodide forms an irreversibly adsorbed and electroinactive layer at gold in the absence of solution iodide, as evidenced by the survival of the 123 and 158 cm⁻¹ SERS bands even at far positive potentials under these conditions. The results obtained for dilute iodide solutions are compared and contrasted with those obtained at higher iodide concentrations. For the latter conditions, the observed “surface” Raman spectra arise from resonance enhancement of the thick insoluble iodine films and solution triiodide formed in the convective diffusion layer rather than from SERS of species present in the double layer. Criteria for distinguishing between these two possibilities for systems involving such electrogenerated species are described.     

Direct electrochemistry of pentachlorophenol hydroxylase

The direct electrochemistry of the flavin-containing monooxygenase, pentachlorophenol hydroxylase (PCPH), at an edge plane graphite electrode was observed and a catalytic response, linear with concentration, was found with the substrate pentachlorophenol (PCP).     

Direct electrochemistry of myoglobin in a layer-by-layer film on an ionic liquid modified electrode containing CeO2 nanoparticles and hyaluronic acid

We describe an ionic liquid modified electrode (CPE-IL) for sensing hydrogen peroxide (HP) that was modified by the layer-by-layer technique with myoglobin (Mb). In addition, the surface of the electrode was modified with CeO₂ nanoparticles (nano-CeO₂) and hyaluronic acid. UV-vis and FTIR spectroscopy confirmed that Mb retains its native structure in the composite film. Scanning electron microscopy showed that the nano-CeO₂ closely interact with Mb to form an inhomogeneously distributed film. Cyclic voltammetry reveals a pair of quasi-reversible redox peaks of Mb, with the cathodic peak at ?0.357?V and the anodic peak at ?0.269?V. The peak separation (??E _p) and the formal potential (E ^0??) are 88?mV and ?0.313?V (vs. Ag/AgCl), respectively. The Mb immobilized in the modified electrode displays an excellent electrocatalytic activity towards HP in the 0.6 to 78.0???M concentration range. The limit of detection is 50?nM (S/N?=?3), and then the Michaelis-Menten constant is 71.8???M. We believe that such a composite film has potential to further investigate other redox proteins and in the fabrication of third-generation biosensors.

Direct electrochemistry and electrocatalysis of myoglobin based on silica-coated gold nanorods/room temperature ionic liquid/silica sol-gel composite film

A novel biosensor based on the silica-coated gold nanorods (GNRs@SiO₂) and hydrophilic room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium tetrafluroborate ([bmim][BF₄]) was fabricated for the determination of hydrogen peroxide (H₂O₂) and nitrite. GNRs@SiO₂ can not only act as a binder to hinder [bmim][BF₄] (RTIL) leaking from the electrode surface, but also provide a favorable microenvironment for direct electrochemistry of myoglobin (Mb). A pair of well-defined and quasi-reversible redox peaks of Mb was obtained at the GNRs@SiO₂-Mb/RTIL-sol-gel composite film modified GCE (GNRs@SiO₂-Mb/RTIL-sol-gel/GCE) through direct electron transfer between Mb and the underlying electrode. This biosensor showed an excellent electrocatalytic activity towards hydrogen peroxide and nitrite. The linear range for the determination of H₂O₂ was from 0.2 to 180 μM with a detection limit of 0.12 μM based on the signal-to-noise ratio of 3. In addition, the biosensor also exhibited high selectivity, good reproducibility, and long-term stability. Therefore, this kind of composite film can provide an ideal matrix for protein immobilization and biosensor fabrication.     

Lithium insertion into TiO2 (anatase): electrochemistry,Raman spectroscopy,and isotope labeling

This article presents a critical discussion of selected structural aspects of electrochemical Li-insertion into TiO₂ (anatase). Recent works are reviewed (almost half of the cited works is from 2010+) with a special attention to the crystal-face-specific phenomena, Raman spectroscopy, and single-crystal and nanocrystalline electrodes. The benefits of isotopic labeling are highlighted for the in-depth understanding of Raman spectra and the Raman spectroelectrochemistry of Li-insertion. The persisting open questions and contradictory issues in the field are discussed too.